(a) A student studied the structure of a mammalian heart. The student took a photograph of the left side of a dissected heart as shown in Fig. 6.1. Identify two features of the left side of the heart visible in Fig. 6.1 and explain how each feature is adapted to the function of the heart. (b) Cardiac muscle is described as myogenic. This means the electrical activity controlling the rhythm of a regular heartbeat begins within the muscle tissue of the heart. Describe how electrical activity within the heart controls each heartbeat. (c) Tissue fluid is formed from blood plasma as it flows through capillaries. Fig. 6.2 is a diagram of a capillary and some adjacent tissue cells in a capillary network. (d) Measles is a common disease caused by a virus. Vaccination to prevent the disease has been very successful.